In the United States, methicillin-resistant Staphylococcus aureus (MRSA) caused 94,360 serious infections and 18,650 deaths in 2005. The number of annual deaths caused by MRSA infection is now higher than that caused by HIV/AIDS (Klevens et al. (2007) Public Health Rep., 122:160-166). Bacterial resistance rendered traditional antibiotics ineffective, adding an unwanted burden to medical care. As a consequence, it is critical to develop a new generation of antibiotics that can eliminate superbugs such as MRSA by a mechanism different from those of traditional antibiotics.